The present invention relates generally to optical devices and, more particularly, to optical assemblies and associated methods for aligning optical components with respect to a light path.
Recent developments in optical communication systems have given rise to miniaturized optical devices that include very small optical components, most of which must be aligned to micron-scale tolerances. For example, in an optical transmitter for optical communications, the output from a light source, such as a laser diode chip, is focused through a lens and coupled into an optical fiber. If a single mode fiber is used in this exemplary optical transmitter, a displacement of the optical fiber by one micron from the ideal aligned position with respect to the laser diode and lens may result in a 50% or more reduction in the optical intensity coupled into the optical fiber. Therefore, the precise alignment of optical components within the miniaturized optical devices is crucial. Furthermore, once the optical components are aligned with respect to each other, it must be possible to secure the optical components in their aligned positions.
Currently, several techniques are available in the alignment and affixation of optical components in miniaturized optical devices. For instance, the optical components may be manually moved into position then fixed onto a mounting pad by using an adhesive or by laser welding, in the case of metalized optical components or, for example, an optical fiber held in a metal sleeve or jacket. The alignment of optical components is generally performed in one of two ways: passive alignment or active alignment.
In the passive alignment technique, a number of device pits and/or grooves are formed in a mounting block on which the optical components are to be supported. The size and position of the device pits and grooves are predetermined according to the specific optical components and the desired alignment configuration such that the optical components, when mounted and fixed in the appropriate device pits and grooves. will automatically be in their aligned positions. Some examples of such passive alignment techniques are commercially available microbench assemblies and v-groove sub-assemblies.
The passive alignment technique presents a number of challenges. High precision fabrication of the optical components as well as the mounting slots and grooves are required to ensure the exact positioning of the optical components relative to each other. If there are slight misalignments, fine adjustments are usually not possible in the passive alignment scheme because the optical components are fixed in their respective slots and grooves. Furthermore, existing passive alignment schemes generally use a wet etch technology to fabricate the mounting slots and grooves. Since the shape of features formed by wet etching depends on the crystallographic plane of the substrate, the use of wet etch technology imposes limitations on the size, shape and formation precision of the mounting slots and grooves, thus potentially leading to inaccuracies in the optical component alignment.
The active alignment technique is more flexible than the passive alignment schemes in that the exact position of the individual optical component can normally be adjusted to fine tune the alignment of that optical component with respect to other components on the substrate. An example of an active alignment system is the Cronos 3D fiber aligner based on a thermal arched beam micro-electromechanical valve (see U.S. Pat. No. 6,114,794 issued to Dhuler et al). The Cronos system uses micro-electromechanical systems (MEMS) technology to provide positioning adjustments in three directions to align, for example, an optical fiber with respect to a laser diode. The optical component is mounted on a movable base which is connected to directional actuators that adjust the position of the movable base, and thus the optical component, by thermally-induced movement with respect to a mounting base.
MEMS devices, such as the Cronos system, are based on fast micro-machining using plasma etching methods. Plasma etching is a dry etch technology which exhibits no crystallographic plane dependency in the shape and depth of etching. Deep etch features with clean edges and excellent verticality are possible with plasma etching technology, thus enabling the manufacture of miniature but complex active alignment systems.
The currently available, active alignment technologies have certain drawbacks. Typically, these systems are bulky and complex in comparison to the passive alignment systems due to the use of separate actuators. Furthermore, most of these systems do not provide a mechanism to fix the actuators, and thereby the optical component, in an aligned position. Accoridingly, constant adjustment of the actuators is required to correct for potential drifts in the optical component position. Although the continual adjustment may be automatically performed by a feedback arrangement, such additional features add to the cost and complexity of the alignment system.
In another aspect of the prior art, certain optical arrangements (not shown) includes a light source and a photodetector, which is intended to detect light emitted by the light source. The photodetector and the light source are normally fabricated on two separate substrates. The light source emits light in a direction generally parallel to the light source substrate, and the photodetector is usually designed to detect light incident on the photodetector along a normal to the photodetector substrate. Therefore, in order to use the photodetector to detect light emitted by this light source, the photodetector substrate must be oriented at a right angle with respect to the light source substrate. The orientation of the light source with respect to the photodetector must be adjustable to provide the optimum coupling of light from the light source into the photodetector. This prior art arrangement thus requires the handling and processing of two separate components with their respective substrates and electrical connections.
The present invention provides an optical assembly which serves to resolve the problems described above with regard to prior art optical assemblies for alignment of optical components in a heretofore unseen and highly advantageous way and which provides still further advantages.
Accordingly, the present invention relates to a device for aligning a first optical component on a substrate with a second optical component comprising: arm means pivotally connected to said substrate, said arm means being pivotable in every direction; holding means for connecting the first optical component to said arm means; and actuator interface means on said arm means enabling manipulation of said arm means by an actuator.
Another aspect of the present invention relates to a method for aligning a first optical component on a substrate with a second optical component comprising the steps of:
providing arms means pivotally connected to the substrate, said arm means having holding means for connecting the optical component thereto, and actuator interface means enabling manipulation of said arm means by an actuator;
aligning the first optical component with the second optical component using the actuator to manipulate the position of said arm means; and
fixing said arm means to the substrate when the first optical component is aligned with the second optical component.